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Upgrade to ProDetect SiYuan Attribute View Asset Cell Stored XSS to RCE (CVE-2026-50551) in IBM QRadar
Detects exploitation of CVE-2026-50551, a stored Cross-Site Scripting (CWE-79) vulnerability in SiYuan (github.com/siyuan-note/siyuan/kernel) affecting versions prior to 0.0.0-20260628153353-2d5d72223df4. Unsanitized attribute view asset cell content allows an attacker to inject malicious script/HTML that executes in the context of the SiYuan kernel's rendering surface, which can be chained with SiYuan's local kernel API and plugin/asset execution surfaces to achieve remote code execution. Detection focuses on suspicious payloads written into attribute view (database) asset cell fields, anomalous kernel HTTP API calls consistent with XSS-to-RCE chaining, and post-exploitation process/file activity on hosts running the SiYuan kernel service.
MITRE ATT&CK
QRadar Detection Query
SELECT DATEFORMAT(devicetime,'YYYY-MM-dd HH:mm:ss') AS EventTime, sourceip, "URL", payload
FROM events
WHERE ("URL" ILIKE '%/api/av/%' OR "URL" ILIKE '%/api/attributeView/%' OR "URL" ILIKE '%/api/asset/%')
AND (payload ILIKE '%<script%' OR payload ILIKE '%onerror=%' OR payload ILIKE '%onload=%' OR payload ILIKE '%javascript:%' OR payload ILIKE '%document.cookie%' OR payload ILIKE '%eval(%')
AND devicetime > NOW() - INTERVAL '24' HOURS
ORDER BY devicetime DESCIdentifies HTTP payloads sent to SiYuan kernel attribute view or asset API endpoints containing script injection markers consistent with the CVE-2026-50551 stored XSS vector.
Data Sources
Required Tables
False Positives & Tuning
- Benign payloads containing similar substrings from note content unrelated to exploitation
- Authorized security assessments testing the same endpoints
- Proxy logging truncation causing partial pattern matches
Other platforms for CVE-2026-50551
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Inject stored XSS payload into SiYuan attribute view asset cell
Expected signal: HTTP POST request to /api/av/setAttributeViewCell containing an <img onerror=...> payload in RequestBody, logged in proxy/access logs.
- Test 2Render malicious attribute view cell to trigger stored XSS
Expected signal: Kernel API request to render the attribute view; if a headless/WebView renderer is used, outbound network telemetry to attacker.example may be observed.
- Test 3Simulate XSS-to-RCE chain via local plugin/script execution
Expected signal: Process creation event for bash/curl spawned in close temporal proximity to the SiYuan kernel process, plus a network connection attempt to an external/test host.
- Test 4Windows lab validation of downstream process spawn after payload render
Expected signal: Sysmon Event ID 1 (Process Creation) for powershell.exe with a benign command line, occurring shortly after a simulated attribute view API request.
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